1. Field of the Invention
This invention relates to a vibration wave motor or a vibration wave apparatus for driving a driven member with a vibration wave motor as a driving source.
2. Related Background Art
As a vibration wave apparatus, there has heretofore been put into practical use a travelling wave type vibration wave motor utilizing flexural vibration generated on an elastic member made of a metal or the like formed, for example, into a ring-like shape or the like, or a bar-like vibration wave motor utilizing the flexural vibration of a vibration member formed into a bar-like shape.
On the other hand, the technique of connecting a plurality of vibration wave motors together to make output torque great has also been proposed (Japanese Patent Application Laid-open No. 9-37573).
Now, a vibration wave motor has as a basic construction a vibration member in which driving vibration is generated, and a contacting member which is provided in press contact with the vibration member. When, for example, the vibration member is a stator, it becomes necessary in utilizing the vibration wave motor as a driving source to fix the vibration member to a fixed member such as a motor case by some method.
For example, in the case of a ring-like vibration wave motor, a ring-like vibration member as a stator is not fixed to a motor case in the outer peripheral portion thereof, and the meshing engagement between a projection formed on the outer diametrical portion of the stator and a groove formed in the inner side of the case provides a rotation stopping mechanism. It utilizes a so-called spline mechanism.
Therefore, the stator is freely movable in a gap formed in the meshing portion between the projection and the groove which constitutes spline coupling and, as a result, there has been a case where backlash occurs there.
Therefore, even if an attempt was made to accurately control the rotation of the contacting member as a rotor, the rotor could not be controlled with accuracy equal to or less than the error due to backlash in movement of the stator/vibration member.
Also, when the outer diametrical portion of the stator and the motor case are fixed, it is conceivable that of vibration in the stator will propagate to the motor case, energy loss will be increased, and the driving efficiency of the motor will deteriorate or the vibration which propagates to the motor case may adversely affect a sensor such as an encoder and surrounding instruments in the form of noise.
Also, there has heretofore been put into practical use as a vibration wave apparatus a travelling wave type vibration wave motor in which an electromechanical energy conversion element, such as a piezoelectric element, adhesively secured to an elastic member made of a metal formed, for example, into a ring-like shape or the like is used as a vibration member and which utilizes flexural vibration excited in the vibration member by a driving signal, such as an alternating signal, being applied to the piezoelectric element, or a bar-like vibration wave motor utilizing the flexural vibration of a vibration member formed into a bar-like shape.
As a system for supporting and fixing the vibration member in the ring-like travelling wave type vibration wave motor, there has been proposed structure in which the vibration member is supported on felt disposed in a motor case to thereby prevent the propagation of vibration to a fixed portion for fixing the vibration member to the case, or structure in which a vibration member itself is made into a ring-like shape and a fixed portion disposed inside it and the vibration member are connected together by a thin plate (sometimes the vibration member and the thin plate and further the fixed portion are made as a unit) to thereby prevent the propagation of vibration to the fixed portion.
On the other hand, with respect to the supporting and fixing features of the vibration member in the bar-like vibration wave motor, there has been proposed structure in which a thin bar (pin) is used coaxially with the bar-like vibration member to connect the vibration member and a fixed portion together and thereby prevent the propagation of vibration to the fixed portion.